Losing coolant but not in bilge

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Peterclayton68

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Hi All

I'm after some help, Over the winter we did a full raw water coolant system rebuild (strip, clean and rebuild) as we had overheating problems last year and not had the time to head out and test until today. We were out for a good 3-4 hour, with some cursing at WOT but mostly at 2500rpm, boat ran great, temps solid at about 82deg C. We stopped 1/2 way and did a quick bilge check and levels to be on the safe side. All good apart from both levels had dropped to the MIN level. Having read that this is normal we continued back to our mooring. Did another check and the starboard engine had dropped down further. I have topped it back up to 1/2 way between MIN and MAX which took 600ml of water. Is this normal, i.e. air pockets being blead or am i losing coolant somewhere? No evidence in the bilge, all dry.

Any sugestions?

Peter
 
No idea whether it's ‘normal’ but I had similar after draining the fresh water system. Is the stbd engine connected to a calorifier by chance?
 
Hi Jamie, no it's the starboard engine. Port engine is connected to Calorifier. I guess I'm worrying over nothing as 600ml is only 3% of total coolant as the Kads take 20ltrs. I will continue to monitor and feedback anything new i find.
 
Mr Googler said:
Normal. Until the stat opens…..you don’t fill all the places.

if you need to do it again….maybe not normal
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I will be heading out again tomorrow, if i need to top up again, then i have a leak. I just need to find it. Hopefully it's nothing serious like, head gasket or cylinder liner seals etc....
 
westernman said:
May be your heat exchanger is leaking from fresh water side into the seawater side??

More probably air pockets though.
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Possible, i did a pressure test on both heat exchangers when i reconditioned them, sea water and fresh water side, no pressure drop. But, that doesn't mean that there not leaking now though.
 
Peterclayton68 said:
Hi All

I'm after some help, Over the winter we did a full raw water coolant system rebuild (strip, clean and rebuild) as we had overheating problems last year and not had the time to head out and test until today. We were out for a good 3-4 hour, with some cursing at WOT but mostly at 2500rpm, boat ran great, temps solid at about 82deg C. We stopped 1/2 way and did a quick bilge check and levels to be on the safe side. All good apart from both levels had dropped to the MIN level. Having read that this is normal we continued back to our mooring. Did another check and the starboard engine had dropped down further. I have topped it back up to 1/2 way between MIN and MAX which took 600ml of water. Is this normal, i.e. air pockets being blead or am i losing coolant somewhere? No evidence in the bilge, all dry.

Any sugestions?

Peter
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As others have said, not unusual after a fresh fill of coolant. Should settle down after a second run out. I keep mine (VP) on the minimum mark of the header tank when cold and it will often be at the mid point when hot so there is always some variation.

www.solocoastalsailing.co.uk
 
Peterclayton68 said:
Oil level was check the first time and was ok, not have not check recently, will do tomorrow morning.
Would the oil emulsify and be milky with water?
Would this be the cylinder liners if water is in the oil?
Thank you all BTW
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You haven’t disturbed the liners ?
Some engines cylinder liners seals are sensitive to the closed coolant quality .But talking aged yrs and old redundant coolant that’s never changed .Ideally use manufacturers type correct concentration and regular change or at least header tank vol replacement if you fear all this air pocket malarkey. How ever it’s got new coolant in now from the drain down to do the coolers i am assuming you did not just refill it with what came out ??

Should coolant enter the oil it’s vol rises on the stick and eventually not the first day emulsified oil will show up under the filler cap as the steam boils off it rise settles under the cap .

As others have said one run out in relation to air pocket elimination and small tops up needed is far too soon to be jumping in with a dooms day diagnosis.It needs bleeding through and re filing for a few runs out .

On the subject of bleeding , getting rid of air pockets the exhaust turbo being situated normally high needs paying particular attention as localised air pockets = bearing failure.
You could from cold warm it up , get a bit of pressure in the system for 10 mins at idle ( stay away from turbo boost ) and open a bleed screw on the turbos see what hisses out ..….hopefully neat coolant not air .

I had a KAD300;once .Opening the stat box and changing it , then arbitrarily topping up “ lost “ coolant via the header tank made no difference to the level when running .Ie the stat box being on top more or less of the block did not seem too prone to air pockets or it simply burped its self out via the header tank which level settled after a run.

They basically are designed to self burp out via the header tank in 95 % of the spaces .But even with best engineering theres always air pockets which eventually can cause the symptoms you are experiencing.
So it needs a few more runs , the highest point ( usually the E turbo ) venting and a careful eye on the tank level .
 
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On both my present Yanmars and previous Volvos. The coolant overflow/expansion bottle was virtually empty when cold but was almost full when engine was hot and/or running.
Any filling of the bottle when cold merely resulted in the extra water being dumped into the bilge.
 
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Portofino said:
You haven’t disturbed the liners ?
Some engines cylinder liners seals are sensitive to the closed coolant quality .But talking aged yrs and old redundant coolant that’s never changed .Ideally use manufacturers type correct concentration and regular change or at least header tank vol replacement if you fear all this air pocket malarkey. How ever it’s got new coolant in now from the drain down to do the coolers i am assuming you did not just refill it with what came out ??

Should coolant enter the oil it’s vol rises on the stick and eventually not the first day emulsified oil will show up under the filler cap as the steam boils off it rise settles under the cap .

As others have said one run out in relation to air pocket elimination and small tops up needed is far too soon to be jumping in with a dooms day diagnosis.It needs bleeding through and re filing for a few runs out .

On the subject of bleeding , getting rid of air pockets the exhaust turbo being situated normally high needs paying particular attention as localised air pockets = bearing failure.
You could from cold warm it up , get a bit of pressure in the system for 10 mins at idle ( stay away from turbo boost ) and open a bleed screw on the turbos see what hisses out ..….hopefully neat coolant not air .

I had a KAD300;once .Opening the stat box and changing it , then arbitrarily topping up “ lost “ coolant via the header tank made no difference to the level when running .Ie the stat box being on top more or less of the block did not seem too prone to air pockets or it simply burped its self out via the header tank which level settled after a run.

They basically are designed to self burp out via the header tank in 95 % of the spaces .But even with best engineering theres always air pockets which eventually can cause the symptoms you are experiencing.
So it needs a few more runs , the highest point ( usually the E turbo ) venting and a careful eye on the tank level .
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Thank you, I bought the boat in 2019, so not sure what coolant was used. We have replaced it with new manufacturer recommended coolant, but can’t vouch for the history. We’re out again today so will keep a close eye on it.
 
After a coolant flush on the KAD's i've worked on.... After filling up initially and running from a while, there will always be a 'burp'; completely normal IMHO.

As mentioned before, the expansion tank rises when hot (hence the name). I leave all my KAD's at the 'min' mark which raises a bit when hot.... never had any issues. Feedback from here previously suggests the expansion tanks are a little too small.
 
As above, burping quite normal. Also the expansion tank caps are desiged to release pressure at a certain point and just like thermostats on rare occaisions they can fail and should be considered a maintenance item alongside exhaust risers etc There are 2 kinds for the KAD range but this is mostlikely yours unless you have the 42. At 30 quid just change them if in doubt. Keypart
Although not your case, I have had an air bubble burped under my thermostats. This can cause the circulation pump to cavitate and not circulate. Not your case because I thought it might be a air bleed issue between the thermostat housing and expansion tank or thermostat housing and turbo but it turned out to be the calorifier. Particularly if it's set for too high a temp or you have drained the system and it wasnt filled properly on refill. If the circulation pump cavitates it will not self burp as the thermostats will remain cold-ish while the engine rapidly overheats. This will usually trigger the overheat alarm within a few hundred yards and is a giveaway you have circulation pump issues.
 
Peterclayton68 said:
Is this normal, i.e. air pockets being blead or am i losing coolant somewhere? No evidence in the bilge, all dry.

Any sugestions?

Peter
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Sometimes air gets trapped in the calorifier if fitted when draining and this can take a while to remove. One way to help the air out of the calorifier if the entries are on the side is to bring the engine up to temperature then stop it and slacken of the uppermost connection to the cooling system on the calorifier, this lets the pressure force the air out. Might have to do this more than once if lots of air
 
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BruceK said:
As above, burping quite normal. Also the expansion tank caps are desiged to release pressure at a certain point and just like thermostats on rare occaisions they can fail and should be considered a maintenance item alongside exhaust risers etc There are 2 kinds for the KAD range but this is mostlikely yours unless you have the 42. At 30 quid just change them if in doubt. Keypart
Although not your case, I have had an air bubble burped under my thermostats. This can cause the circulation pump to cavitate and not circulate. Not your case because I thought it might be a air bleed issue between the thermostat housing and expansion tank or thermostat housing and turbo but it turned out to be the calorifier. Particularly if it's set for too high a temp or you have drained the system and it wasnt filled properly on refill. If the circulation pump cavitates it will not self burp as the thermostats will remain cold-ish while the engine rapidly overheats. This will usually trigger the overheat alarm within a few hundred yards and is a giveaway you have circulation pump issues.
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For £30 for a cap, it's a simple change part.
 
Peterclayton68 said:
For £30 for a cap, it's a simple change part.
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If the caps lost it’s seal there will be witness marks of dry coolant around it .

For the record MAN from circa 2000 have “ coolant expansion pressure “ on a the dash …..so you can monitor the air pressure in the header tank ……and tell if the caps are leaking it drops or some other thing it increases is out of spec .
Just saying guys .

25DABF1E-35A1-44E9-B407-2494B2D22C5F.jpeg
As can see bombing through the Golf of St Tropez -coolant expansion pressure 700 mbr no codes thrown. That’s the air pressure above the coolant in the header tank .
Nice to know .
The 2.7 bar coolant pump pressure tells me the impeller is ok too .

Why others do not fit this stuff baffles me!
You are flying blind.
 
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